I reckon legally a tow bar on the front would need engineering in NSW, the nanny state when it comes to car mods, although I know other states are pretty bad too these days. I had one on an old AP6 valiant wagon I owned for years, never needed to use it myself but fellow before me used it to reverse trailer/boat into tight spots. On an older fairlane - no way I would do that for so many reasons, legality being just one.
Back to the issue at hand, I'm actually finding it hard to understand where we are at at the moment. My take is
New house , difficult driveway
One boat on trailer
Second trailer - wider than boat and other trailer
Boat and trailer # 1 successfully in yard by driving in and unhooking, car turned around and driven out
Trailer # 2 now finding a way to reverse it into same yard thru same driveway but clearance an issue
Was there a reason you couldn't just drive trailer #2 in as well, unload then turn car around again?
Hope I am not confusing the matter more, Maybe I need to take up drinking again, been about 6 weeks since my last :-)
Muz